1. Field of the Invention
The field of art to which this improvement pertains includes a synchronizer assembly for toothed clutches in speed change transmissions having gears which are constantly in mesh, particularly for motor vehicles and the like for clutching either of a pair of gears to a shaft on which the gears are rotatably journalled.
2. Description of the Prior Art
The form of clutch synchronizer assemblies to which this invention is applicable includes an axially slidable clutch collar member that is mounted on a splined portion of a shaft on which a pair of axially spaced gears are rotatably mounted. The clutch collar member is provided with jaw clutch teeth which are adapted to be disposed in engagement with jaw clutch teeth formed on the rotatable gears for positively clutching either one of the gears to the shaft. The clutch collar member is formed with a radially extending flange having a plurality of circumferentially spaced openings therethrough and parallel to the shaft. Disposed through certain ones of these openings are pins which are fixed at their ends and synchronizer rings that are adapted to cooperate with the aforesaid gears. The pins have reduced central portions which define shoulders that are adapted to cooperate with the flange opening edges for blocking relative axial movement of the latter with respect to the synchronizer rings when they are rotating asynchronously. Disposed through others of said flange openings are a plurality of longitudinally split pin assemblies which are freely received at their ends in recesses formed in the synchronizer rings. The split pin assemblies are formed with central annular grooves which are biased into engagement with the peripheries of the openings in the clutch collar member flange by resilient means disposed between portions of each pin assembly. Upon initial axial movement of the clutch collar member, the synchronizer rings are caused to move conjointly therewith by the split pin assemblies. After one of the synchronizer rings has been disposed in clutching engagement with the adjacent gear and synchronous speed is attained between the gear and the clutch collar member, further axial movement of the latter will cause the portions of the split pin assemblies to compress or collapse, which cocks the latter and effects snap judgment of the jaw clutch teeth of the clutch collar member with the jaw clutch teeth of the gear.
An example of one prior art synchronizer which is widely used is disclosed and claimed in U.S. Pat. No. 2,667,955 to Bixby, dated 2 Feb. 1954 which is assigned to the same assignee as the present invention. Further prior art patents of this type include U.S. Pat. No. 3,078,975 to Eaton and U.S. Pat. No. 3,910,390 to Eichinger.
While the Bixby synchronizer assembly has been widely used and has been very successful, certain problems, about to be described, have remained, which problems have been recognized and solved by the present invention.
The most serious problem associated with this prior art synchronizer is the occasional incomplete return to the neutral position of the intermediate collar member upon its disengagement from either of its associated gears. While further gears (other than those associated with this particular synchronizer) can readily be shifted, upon the operator's attempt to shift back into the gear from which there was an incomplete return to the neutral position, there can be no force transfer from the collar member through the split pin assemblies to the synchronizer ring. In the absence of the required angular displacement of the clutch collar relative to the synchronizer ring, the blocker pins do not block and the shift into the gear will be accomplished without the benefit of synchronization which cna result in serious clashing problems accompanied by excessive noise and possible losses of portions of the clutching teeth.
A further problem has been known to occur in the form of excessive ramp wear at the intersections of the dual ramps associated with the blocker pin grooves. While it may seem obvious to harden these steel pins, they could only be induction hardened in the groove areas since the outer ends of the pins have to be soft enough to permit their subsequent riveting to the synchronizer rings which, of course, precludes case hardening.
An additional prior art problem is that the spring members between the split pins are compressed during the relative angular displacement between the clutch collar member and the synchronizer rings which, together with the use of high rate spring members, produced a set in these spring members after a limited number of cycles.
A yet further problem is that the diametral extent of the synchronizer ring recesses are insufficient to permit the previously-described angular movement without compressing the spring members thereby again causing premature spring set.